Electric hot water circulating pump with motor having an axial air gap

ABSTRACT

In an electric pump used for the circulation of hot water the inductor of the moor is formed by a stator of the front type and the armature consists of a fixed magnetic part and a movable disc of material having a high conductivity keyed onto the end of the shaft, onto the opposite end of which the pump impeller is keyed. By separating in this manner the electrical circuit of the rotor from the magnetic circuit the axial thrust is eliminated.

United States Patent 11 1 1111 3,767,330 Signorile Oct. 23, 1973 [54]ELECTRIC HOT WATER CIRCULATING 547,069 /1895 Gorges 310/268 PUMP WITHMOTOR HAVING AN AXIAL 2,378,556 6/1945 Jeffers 310/268 AIR GAP 2,512,34610/1947 Lenehan 310/268 2,730,953 1/1956 Pensabene 417/420 [75]inventor: Marco Signorile, Milan, Italy 2,782,721 2/1957 White 310/2683,060,337 10/1962 Henry-Bandot. 310/268 1 Asslgneei Ercole Marci" & -P-Rome, 3,069,577 12 1962 Lee 1. 310/268 Italy 3,304,450 2/1967 Bosco310/268 3,333,544 8/1967 Turk 310/86 [22] Fhed" 1971 3,355,914 12/1967Venema 310/268 [211 APPL 1731362 FOREIGN PATENTS OR APPLICATIONS 748,7085/1956 Great Britain 417/420 Foreign Application Priority Data 978,68312/1964 Great Britain... 417/420 995 386 8/1951 France 417/420 4 1 A 71L 3; fi i :3 1 1,502,641 10/1967 France 417 420 1 a y 1,527,434 4/1968France 310/160 Primary Examiner wimam L. Freeh [58] Field of Search417/420, 348-356,

417/357, 410; 310/268, 86 ABSTRACT [56] References Cited In an electricpump used for the circulation of hot UNITED STATES PATENTS water theInductor of the moor 15 formed by a stator of the front type and thearmature consists of a fixed 1,590,025 6/1926 l1:2111 m g p and amovable disc of material having a .4 high conductivity keyed onto theend of the shaft, 2:693:140 11 1954 White 417/410 the Opposite ehd whichthe Pump impel]elr is 1,780,337 11 1930 Canton 417 357 y 2,248,0307/1941 Zwack 417/420 B eparating in this manner the electrical circuitof 1 x the rotor from the magnetic circuit the axial thrust is artm ated3,420,184 1/1969 Englesberg. 417/420 m M 3,429,137 2/1969 Law 417/420 7Claims, 2 Drawing Figures PATENTEDHBI 23 um 3.767; 330

' SHEET 2 OF 2 Fig.2

INVE NTOR mflf SIG-NOK/LE MQLW fiTTOF N YS 1 ELECTRIC HOT WATERCIRCULATING PUMP WITH MOTOR HAVING AN AXIAL AIR GAP The electric pumpsused for the circulation of hot water in heating systems and for thedistribution of hot water in household premises are comprised, in theirmost widespread form at present, of a centrifugal pump actuated by anasynchronous motor whose cage rotor is immersed in the same watercirculating in the pump.

The main object of this construction is to avoid leakages of water tothe exterior as a consequence of using seals between fixed and rotatingparts with reduction to a minimum of the static torque at starting.

The basic problem which must be solved however in the construction ofthese electric pumps, lies in the separation of the rotary part of themotor, immersed in the liquid, from the static part which mustnecessarily be dry in order to preserve the winding insulation.

This separation can be obtained in a'particularly simple and safe mannerby using motors of the axial air gap type, because in this case for theseparation between rotor and stator a flat diaphragm arranged in the airgap is sufficient, while the sealing members are reduced to thosenormally used in reliably fluidtight and lasting flange joints.

Unfortunately axial air gap motors have a thrust which'acts in thedirection of the axis of rotation on account of the attraction occurringbetween the magnetic packs or stacks of stator and rotor.

The magnitude of this thrust is considerable and the operation of themotors can be achieved only on the condition that there are providedsuitable mechanical support members for taking up the axial thrust.

When it is not possible to use ball bearings, and this is the, case withmotors for the above-mentioned circulation pumps, it is necessary tohave recourse to constructional complications and limitations whichcancel out the advantages obtainable with these types of motor.

The present invention relates to an electric hot water circulating pumpoperated by a special motor with axial air gap, completely without axialthrust which has, therefore, all the advantages of this type of motorfor the particular application but without having its disadvantages.

More particularly the electric hot water circulating pump in accordancewith the invention is characterised in. that it is comprised of acentrifugal pump operated by an asynchronous motor, whoseinductor ifformed by a stator of the front type and whose armature consists of 'afixed magnetic part and of a movable disc of material with highconductivity keyed onto the end of shaft, onto the opposite end of whichthe pump impeller is keyed.

The elimination of the axial thrust is achieved in accordance with theinvention by separating the electrical rotor circuit from the magneticcircuit. The electrical rotor circuit is the only rotary part of themotor free to rotate, keyed onto the shaft, while the magnetic circuitis fixed.

Theattraction occurring between the magnetic stator and rotary parts istherefore taken up by the casing of said rigid and non-deformable parts,while the rotary part having no magnetic material does not undergoattraction or repulsion in axial direction.

This rotary part is formed by a disc of material having goodconductivity, drawn and shaped for the purpose of increasing themechanical strength.

The rotor disc is fitted and locked onto the shaft which supports thepump impeller and is kept at a fixed distance from the front surface ofthe magnetic part by the axial thrust produced by the pump opposed by asuitable backing washer.

In accordance with a feature of the invention the magnetic part of thearmature is comprised of a magnetic stack obtained by a spirally woundstrip of steel sheet.

It has been found however that it was possible to obtain a notablesaving in the construction of the magnetic part of the armature.

Therefore in accordance with another feature of the invention themagnetic part of the armature is formed from the same material used forthe construction of the shield which holds it and produced by formingand machining simultaneously with the shield itself.

According to a further feature of the invention the material used forthe construction of the shield and of the magnetic part of the armatureis constituted by cast iron.

According to yet another feature of the invention the material used forthe construction of these parts is constituted by sintered steel.

The invention will be understood more clearly from the followingdescription of two of its embodiments, with reference to the attacheddrawings, in which:

FIG. 1 shows diagrammatically a section through an electric pump inaccordance with the invention along the axis of rotation; and

FIG. 2 shows the same section in another embodiment.

Referring first to FIG. 1, in which 1 designates the intake or suctionduct and 2 the exhaust duct of the pump,3 designates the impeller and 4the shaft common to the rotor and to the impeller, 5 indicates thestator (primary) of the motor in whose radial slots there is arrangedthe winding 6. The secondary or armature of the motor is formed by thefixed magnetic part 7 and by the rotary part 8, consisting of a disc ofmaterial having good conductivity, suitably shaped as shown in thediagram and keyed onto the shaft 4.

The magnetic part 7 consists of a spirally wound strip of steel sheet.

Both the magnetic stator part 5 and the magnetic part 7 of the armatureare rigidly fixed to the respective metal support parts A and B.

The attraction between the magnetic parts is therefore taken up by theaforesaid support parts which are fixed and interlocked.

In FIG. 1 there are also indicated by 12 the sealing rings of flexiblematerial, and by 9 the separation dia-- phragm between the partssubmerged in the liquid and the dry static part this diaphragmconsisting of a thin sheet of non-magnetic material of high resistivity.

There are designated by 10 the holes or ports communicating between thepump circuit and the chamber containing the motor rotor, which holeshave the purpose together with those provided in the rotary disc in theproximity of the hub,of balancing the pressures and allowing acirculation of liquid inside the motor under the centrifugal action ofthe rotating part.

The advantages of the above-mentioned construction concern: economy inconstruction, easy assembling and disassembling for overhaul andcleaning, reliability of operation combined with exceptional quietnessand long life.

The economy in construction is clearly apparent from a simple inspectionof the constructional diagram of FIG. 1 which shows the presence of onlyone support for the shaft, with dimensions reduced to a minimum, whichcarries at one end the rotary part of the motor and at the opposite endthe pump impeller, the constructional simplicity of the armature of themotor, whose rotating part is reduced to a simple shaped disc, while thefixed part is formed by a spirally wound sheet strip, and the simplicityof the members separating the submerged part of the motor from the drypart.

In the same FIG.1 it can be seen how the entire stator part can easilybe detached and removed from the remaining part of the electric pump,how the rotary part of the motor can be removed by loosening a singlescrew and how all the remaining assembly of shaft, impeller andassociated support, can be removed leaving in place the piping and thevolute. It is obvious how the easy disassembly for access to theinternal parts can ensure an easy cleaning and overhaul and thereforereliability in operation.

The special form of the disc-type rotor assures a degree of quietness inthe operation of the motor which cannot be achieved with rotors ofconventional form with rotor cage arranged inside the slots. The life ofthe electric pump which is essentially due to the life of the bearings,to the life of the tightness of the stator part and to the life of thewinding insulation, is ensured by the minimal weight of the rotary part,by the efficiency and simplicity of the separation system between thepart of the motor immersed in water and the dry parts, by the reliablemanufacturing of the windings in a stator of the front type and by thepossibility of replacing all the air gaps between windings and earth, byfilling the stator cavity with a suitable termosetting resin. The shapeof the parts of the motor in contact with the liquid makes these partsadapted to be built in a simple, rational and inexpensive manner withstainless materials, so as to reduce the corrosion which the presence ofthe liquid can tend to cause to negligible values.

The electric pump shown in FIG. 2 differs from that in FIG.1 only asregards the magnetic part of the armature. As for the rest it isidentical to that in FIG.1 and therefore its description will not berepeated.

The magnetic part 7 is solid and made with the same material as thatused for the shield B which holds it, and it is produced by forming andmachining simultaneously with the shield, tha material employedpreferably being cast iron or sintered steel. It is obvious that by aconstruction of this type of the magnetic part of the armature a notablesaving in the manufacture and assembly of the magnetic part with respectto the embodiment in FlG.l, is obtained.

I claim:

1. An electric pump for the circulation of liquid including a pumpimpeller which is positioned within a housing and operated by anasynchronous motor, said motor comprising first and secondaxially-spaced, fixed magnetic stators, a shaft mounting said pumpimpeller on one end thereof, a disc mounted on the other end of saidshaft for rotation between said first and second magnetic stators, saidrotating disc having an axially extending flange at its periphery and adepression formed in the central portion thereof, said flangesurrounding a portion of said first magnetic stator.

2. An electric pump in accordance with claim 1 wherein said firstmagnetic stator is supported by a shield having a central hub, saidshield being provided with holes at its periphery and in the central hubof said shield, said rotating disc including holes formed in saiddepression, wherein in said shield holes and said disc holes balance thepressure of water circulating inside the pump.

3. An electric pump in accordance with claim 2 including a sealingdiaphragm located between said second magnetic stator and said rotatingdisc.

4. An electric pump in accordance with claim 3 wherein said firstmagnetic stator is formed from a roll of rustproof steel having magneticproperties.

5. An electric pump in accordance with claim 3 wherein said firstmagnetic stator and said shield are formed of the same material.

6. An electric pump in accordance with claim 5 wherein said shield andsaid first magnetic stator are formed from cast iron.

7. An electric pump in accordance with claim 5 wherein said shield andsaid first magnetic stator are formed from sintered steel.

Patent: No.

UNITED STATES PATENT OFFICE 330 Dated oetober 23, 1973 Inventor(s) MARCOSIGNORILE (SEAL) lAttest:

RUTH c. MASON Arresting Officer In the priority date, "April 28, 1 to--August 28, 1970--.

It is certified that error appears inthe aFOve-identified patent andthat said Letters Patent are hereby corrected as shown below:

Signed and sealed this 29th day of April 1975.

c. MARSHALL DANN Commissioner of Patents and Trademarks 970' is changed

1. An electric pump for the circulation of liquid including a pumpimpeller which is positioned within a housing and operated by anasynchronous motor, said motor comprising first and secondaxially-spaced, fixed magnetic stators, a shaft mounting said pumpimpeller on one end thereof, a disc mounted on the other end of saidshaft for rotation between said first and second magnetic stators, saidrotating disc having an axially extending flange at its periphery and adepression formed in the central portion thereof, said flangesurrounding a portion of said first magnetic stator.
 2. An electric pumpin accordance with claim 1 wherein said first magnetic stator issupported by a shield having a central hub, said shield being providedwith holes at its periphery and in the central hub of said shield, saidrotating disc including holes formed in said depression, wherein in saidshield holes and said disc hoLes balance the pressure of watercirculating inside the pump.
 3. An electric pump in accordance withclaim 2 including a sealing diaphragm located between said secondmagnetic stator and said rotating disc.
 4. An electric pump inaccordance with claim 3 wherein said first magnetic stator is formedfrom a roll of rustproof steel having magnetic properties.
 5. Anelectric pump in accordance with claim 3 wherein said first magneticstator and said shield are formed of the same material.
 6. An electricpump in accordance with claim 5 wherein said shield and said firstmagnetic stator are formed from cast iron.
 7. An electric pump inaccordance with claim 5 wherein said shield and said first magneticstator are formed from sintered steel.